Roger Ailes, chairman and CEO of Fox News and Fox Television Stations.

"The creation of Fox News was a sea change," said Betsy West, a professor at Columbia University's Graduate School of Journalism. "His graphics were a much more entertaining presentation, but that's a superficial look of what he did. Even more than that, by staking out Fox News as a media outlet attuned to the voices of the political right — including the far right — he really set the stage for our current politicized media landscape."

Sources told CNBC that 21st Century Fox was nearing a decision that would likely end in Ailes' departure. In a statement, 21st Century Fox said Ailes was still at work, and the review was ongoing.

Lawyers for Ailes did not respond to requests for comment.

Ailes began his career as a producer on "The Mike Douglas Show," which eventually became a nationally syndicated talk show. He then moved into political consulting, working with the likes of George H.W. Bush and former Attorney General Dick Thornburgh.

Ailes eventually made his way back to television, this time focusing on cable news. In 1993, he became president of CNBC and later created the "America's Talking" channel, which would eventually become MSNBC. He then was tapped by Rupert Murdoch in 1996 to become CEO of Fox News.

West, who previously was senior vice president at CBS News and an executive producer at ABC News, said that before Fox News, the only model for cable news was CNN's then-style of straight reporting. Ailes began the movement of turning cable news into politically tuned outlets.

"It was the beginning of people going to their own echo chambers, listening to the programming that conformed with their own political thinking," she said.

This blend of politics and talk show theatrics appealed to a demographic of Americans who felt their viewpoints weren't acknowledged by mainstream media. West said Ailes prided himself in "representing anti-elite media."

"That talk show mentality where you really want to create controversy, where you want to create energy, where you want it to be entertaining — like when he worked on 'The Mike Douglas Show' — you can see it when Fox News debuted," she said. "It had a different rhythm to it than CNN."

In the world of cable news, Fox News has been a ratings juggernaut, often coming in first. One media buyer said that while news has never been a huge draw for advertisers because of its typical older viewership, Fox News' large audience numbers made some brands open to advertising on its programming. At the same time, it also scared away some companies who were afraid to be associated with the network's political views.

"It made the news genre more of a consideration than it had been for many, many years," said the media buyer, who asked to remain anonymous.

Gabriel Khan, a professor at the University of Southern California Annenberg School for Communication and Journalism, said what Ailes understood best is that Fox News needed to play to its key audience to win.

"That's really what Fox did: They owned a cable news audience by serving a segment that might have been underserved," Khan said.